Nuts

The results of most prospective cohort studies suggest that
regular nut consumption (equivalent to 1 oz at least five times weekly)
is associated with a significantly lower risk of cardiovascular disease. (More Information)

One prospective cohort study has found that regular
nut consumption is associated with significantly lower risk of
developing type 2 diabetes. (More Information)

Most prospective studies have shown that people who consume nuts regularly weigh less than those who rarely consume nuts. Nonetheless, since an ounce of most nuts provides about 160 kcal of energy,
substituting nuts for other less healthy snacks is a good strategy
for avoiding weight gain when increasing nut intake. (More
Information)

Introduction

In the not too distant past, nuts were considered unhealthy because of
their relatively high fat content. In contrast, recent research suggests
that regular nut consumption is an important part of a healthful diet (1).
Although the fat content of nuts is relatively high (14-19 grams/ounce),
most of the fats in nuts are the healthier, monounsaturated and polyunsaturated
fats (2) (see Table).
The term “nuts” includes almonds, Brazil nuts, cashews, hazelnuts, macadamia
nuts, pecans, pistachios, walnuts, and peanuts. Despite their name, peanuts
are actually legumes like peas and beans. However, they are nutritionally
similar to tree nuts and have some of the same beneficial properties.

Disease Prevention

Cardiovascular Disease

Coronary Heart Disease

In large prospective
cohort studies, regular nut consumption has been consistently associated
with significant reductions in the risk of coronary
heart disease (CHD) (3). One of the
first studies to observe a protective effect of nut consumption was the
Adventist Health Study, which followed more than 30,000 Seventh Day Adventists
over 12 years (4). In general, the dietary
and lifestyle habits of Seventh Day Adventists are closer to those recommended
for cardiovascular disease prevention
than those of average Americans. Few of those who participated in the
Adventist Health Study smoked, and most consumed a diet lower in saturated
fat than the average American. In this healthy group, those
who consumed nuts at least five times weekly had a 48% lower risk of death from CHD
and a 51% lower risk of a nonfatal myocardial
infarction (MI) compared to those who consumed nuts less than once weekly (4). In Seventh Day Adventists who were older than 83 years of
age, those who ate nuts at least five times weekly had a risk of death from
CHD that was 39% lower than those who consumed nuts less than once weekly
(5). A smaller prospective
study of more than 3,000 Black men and women reported similar results (6).
Those who consumed nuts at least five times weekly had a risk of death from
CHD that was 44% lower than those who consumed nuts less than once weekly (6).

The cardioprotective effects of nuts are not limited to Seventh Day
Adventists. In a 14-year study of more than 86,000 women participating
in the Nurses’ Health Study, those who consumed more than 5 oz of nuts
weekly had a risk of CHD that was 35% lower than those who ate less than
1 oz of nuts monthly (7). Similar decreases
were observed for the risk of nonfatal MI and death from CHD. More recently,
a 17-year study of more than 21,000 male physicians found that
those who consumed nuts at least twice weekly had a risk of sudden cardiac
death that was 53% lower than those who rarely or never consumed nuts,
although there was no significant decrease in the risk of nonfatal MI
or nonsudden CHD death (8). A follow-up analysis in this cohort of male physicians found that nut consumption was not associated with incident heart failure (9). The Iowa Women’s
Health Study, which followed more than 30,000 postmenopausal women for
12 years, is the only published prospective study that did not observe
a significant inverse association between nut consumption and CHD mortality,
although a slight but significant decrease in all-cause mortality was
observed in those who consumed nuts twice weekly (10).
Overall, the results of most prospective cohort studies suggest that regular
nut consumption is associated with a substantial decrease in the risk
of death related to CHD. In fact, a recent pooled analysis of four of the U.S. epidemiological studies mentioned above found those with the highest intake of nuts (about 5 times per week) had a 35% lower risk of CHD (11).

Results of controlled clinical trials indicate that at least part of
the cardioprotective effect of nuts is derived from beneficial
effects on serum total and LDLcholesterol
concentrations (3). At least 18 controlled
clinical trials have found that adding nuts to a diet that is low in saturated
fat results in significantly reductions in serum total cholesterol and
LDL cholesterol concentrations in people with normal or elevated serum
cholesterol. These effects have been observed for almonds (12-15),
hazelnuts (16), macadamia nuts (17-19),
peanuts (20, 21), pecans (22),
pistachio nuts (23, 24) and walnuts (25-30).
More recently, a cross-sectional study found that frequent nut and seed consumption
was associated with lower serum levels of inflammatory biomarkers in
a multi-ethnic population (31). Although
the evidence is circumstantial, these findings suggest that compounds
in nuts may lower the risk of cardiovascular disease by decreasing inflammation.

Cardioprotective Compounds
in Nuts

Substituting dietary saturated
fats with polyunsaturated
and monounsaturated
fats like those found in nuts can decrease serum
total and LDLcholesterol
concentrations (3). However, in some clinical trials, the cholesterol-lowering effect of nut consumption
was greater than would be predicted from the polyunsaturated and monounsaturated
fat content of the nuts, suggesting there may be other protective factors
in nuts (32). Other bioactive compounds
in nuts that may contribute to their cholesterol-lowering effects include
fiber and phytosterols(33). See the table below for the unsaturated fat, fiber,
and phytosterol content of selected nuts. Walnuts are especially rich
in alpha-linolenic acid, an omega-3
fatty acid with a number of cardioprotective effects, including the
prevention of cardiac arrhythmias
that may lead to sudden cardiac death. Other nutrients that may contribute
to the cardioprotective effects of nuts include folate, vitamin E,
and potassium(3,
33-35). The U.S. Food and Drug Administration
(FDA) has acknowledged the emerging evidence for a relationship between
nut consumption and cardiovascular disease risk by approving the following
qualified health claim for nuts (36):
“Scientific evidence suggests but does not prove that eating 1.5 ounces
per day of most nuts as part of a diet low in saturated fat and cholesterol
may reduce the risk of heart disease.” For more information on the nutrient
content of nuts, search the USDA
National Nutrient Database.

Energy, Fat, Phytosterols and Fiber in a 1-oz
Serving of Selected Nuts

Nut
(1 ounce)

Energy (kcal)

Total fat (g)

MUFA* (g)

PUFA* (g)

Phytosterols (mg)

Fiber (g)

Almonds

163

14.0

8.8

3.4

39

3.5

Brazil nuts

186

18.8

7.0

5.8

N/A

2.1

Cashews

163

13.1

7.7

2.2

45

0.9

Hazelnuts

178

17.2

12.9

2.2

27

2.7

Macadamia nuts

204

21.5

16.7

0.4

33

2.4

Peanuts (legume)

161

14.0

6.9

4.4

62

2.4

Peanut butter, smooth (2 Tbsp)

188

16.1

7.6

4.4

33

1.9

Pecans

196

20.4

11.6

6.1

29

2.7

Pine nuts (pignoli)

191

19.4

5.3

9.7

40

1.0

Pistachio nuts

158

12.6

6.6

3.8

61

2.9

Walnuts, Black

175

16.7

4.3

9.9

31

1.9

*MUFA, Monounsaturated Fatty Acids; PUFA, Polyunsaturated Fatty Acids

Type 2 Diabetes Mellitus

Recent results from the Nurses’ Health Study suggest that nut and peanut
butter consumption may be inversely associated with the risk of type 2
diabetes mellitus (DM) in women
(37). In this cohort of more than 86,000
women followed over 16 years, those who consumed an ounce of nuts at least
five times weekly had a risk of developing type 2 DM that was 27% lower than
those who rarely or never consumed nuts. Similarly those who consumed
peanut butter at least five times weekly had a risk of developing type
2 DM that was 21% lower than those who rarely or never consumed peanut
butter. While these findings require confirmation in other studies, they
provide additional evidence that nuts can be a component of a healthful
diet. Compounds in nuts that could contribute to the observed decrease
in type 2 DM include unsaturated
fats, fiber, and
magnesium.

Body Weight

A major concern is that increased consumption of nuts may cause weight gain and obesity. However, several cross-sectional analyses of large cohort studies, including the Adventist Health Study (5) and the Nurses' Health Study (7), have shown that individuals who consume nuts regularly tend to weigh less than those who rarely consume them. Recently, a 28-month prospective study conducted in Spain found that participants who consumed higher amount of nuts had lower risk of weight gain than those who rarely ate nuts (38). A similar association was observed in the Nurses' Health Study II (39). These epidemiologic data indicate that in free-living subjects, higher nut consumption does not cause greater weight gain; rather, incorporating nuts into diets may be beneficial for weight control. It is possible that higher amounts of protein and fiber in nuts enhance satiety and suppress hunger.

Safety

Nut Allergies

Allergies to peanuts and tree nuts (almonds, cashews, hazelnuts, pecans,
pistachios, and walnuts) are among the most common food allergies, affecting
at least 1% of the U.S. population (40).
Although all food allergies have the potential to induce severe reactions,
peanuts and tree nuts are among the foods most commonly associated with
anaphylaxis, a life-threatening
allergic reaction (41). People with severe
peanut or tree nut allergies need to take special precautions to avoid
inadvertently consuming peanuts or tree nuts by checking labels and avoiding
unlabeled snacks, candies, and desserts. See the Food
Allergy and Anaphylaxis Network Web site for additional tips to avoiding
unintentional peanut or tree nut exposure.

Adverse Effects

Brazil nuts grown in areas of Brazil with selenium-rich soil may provide more than 100 mcg of selenium in one nut, while those grown in selenium-poor soil may provide ten times less (42). For information regarding toxicity of selenium, please see the article on Selenium.

Intake Recommendations

Regular nut consumption, equivalent to an ounce of nuts five times weekly,
has been consistently associated with significant reductions in coronary
heart disease (CHD) risk in epidemiological
studies. Consuming 1-2 oz of nuts daily as part of a diet that is
low in saturated fat has been found to lower serum total and LDL cholesterol
in a number of controlled clinical
trials. Since an ounce of most nuts provides at least 160 calories
(kcal), simply adding an ounce of nuts daily to one’s habitual diet without
eliminating other foods may result in weight gain. Substituting unsalted
nuts for other less healthy snacks or for meat in main dishes are two
ways to make nuts part of a healthful diet.

Reviewed in June 2009 by:
Frank B. Hu, M.D., Ph.D.
Professor of Nutrition and Epidemiology
Harvard School of Public Health

Copyright 2003-2015 Linus Pauling Institute

Disclaimer

The Linus Pauling Institute Micronutrient Information Center provides scientific information on the health aspects of dietary factors and supplements, foods, and beverages for the general public. The information is made available with the understanding that the author and publisher are not providing medical, psychological, or nutritional counseling services on this site. The information should not be used in place of a consultation with a competent health care or nutrition professional.

The information on dietary factors and supplements, foods, and beverages contained on this Web site does not cover all possible uses, actions, precautions, side effects, and interactions. It is not intended as nutritional or medical advice for individual problems. Liability for individual actions or omissions based upon the contents of this site is expressly disclaimed.